1. Field of the Invention
The present invention relates to a technique for discriminating a change in state of an image input from a camera.
2. Description of the Related Art
Monitoring apparatuses, such as a monitoring camera, which compare a difference between a current image input from a camera and a reference background image to detect any portion of the image that has changed are known. Apparatuses of this type output a signal which is used for a display or a warning on a monitoring screen to notify that an object is left unattended or has been taken away, if the duration for which the change has been detected exceeds a predetermined time (refer to Japanese Patent Application Laid-Open No. 2000-331254).
The apparatus discussed in the Japanese Patent Application Laid-Open No. 2000-331254 uses an object movement detection system, which determines that there is a change when the duration for which the change has been detected exceeds a predetermined time. Accordingly, a warning can be provided regarding the appearance of an object (i.e., the object is left unattended) or the disappearance of an object (i.e., the object is taken away) if detected.
There may be a scene in which an object similar in size moves to the same position at the same time, such as a milk bottle, or a newspaper periodically delivered every morning, a delivery car of a convenience store or a mail truck periodically circulating every day. The appearance and the disappearance of an object as scheduled may have been previously approved, so that it is inconvenient, in view of a monitoring efficiency, for a user to be called to a monitor, or asked to confirm a monitor or visit a questionable site each time an object is left unattended or an object is taken away.
As described above, until now, the appearance and the disappearance of an object, which occurs periodically, could not have been discriminated from the appearance and the disappearance of an object, which occur non-periodically.